[cffi-devel] Re: creating two-dimensional arrays

[hbabcockos1 at mac.com]

On Mar 15, 2006, at 6:46 AM, Luís Oliveira wrote:

> hbabcockos1 at mac.com writes:
>> What is the right way to create a 2D array to pass to a c-function
>> that expects **arr?
>
> In message ID <BAY17-DAV41D78728D384B9C2D15ADD9300 at phx.gbl>, Vasilis
> sent some functions macros to manipulate and create arrays of  
> arbitrary
> ranks: http://common-lisp.net/pipermail/cffi-devel/2005-December/ 
> 000281.html

I was able to get this to work. I was using the wrong index variable  
(y instead of x) in the inner loop.

   (defun make-matrix (lisp-mat)
     "Creates a two-dimensional c array, initializes with lisp matrix"
     (let* ((x-dim (array-dimension lisp-mat 0))
	   (y-dim (array-dimension lisp-mat 1))
	   (c-mat (foreign-alloc :pointer :count y-dim)))
       (dotimes (y y-dim)
	(let ((cur (foreign-alloc :double :count x-dim)))
	  (setf (mem-aref c-mat :pointer y) cur)
	  (dotimes (x x-dim)
	    (setf (mem-aref cur :double x) (coerce (aref lisp-mat x y)  
'double-float)))))
       c-mat))                                         ^^^

Thanks for the suggestion though, it looks like a nice generalization  
of the specific case I am trying to handle.

-Hazen